slowstart..

[TF3CY]

Hi all

I just finished building a HV supply for two of my home built amplifiers..

I purchased an PeterDahl ARRL-02-002 transformer and designed a slow-start circuit around him.

First live tests where conducted yesterday with somewhat good resaults.. Using a variac everything is ok...

I'm working with a 230VAC circuit with a 16A breaker - and I know it is not enough for full utilization of the supply

The slowstart is pretty straight forward - using a timer circuit to close one relay to apply power to the transformer and a secondary delayed relay that shorts out a resistor that is otherwise in series with the mains supply to the transformer.

The mains here in Iceland is either PEN or 2 live phases with 220v between them.. basically just a single phase system.
I used two 47 ohm resistors on each "line" and the double throw relay shorts them both.

The timer is set to around 400ms give or take. - I have not done any adjustment of the timer - but bit long.


So when I give the HV the control signal I sometimes trigger the breaker - during the AC peak voltage period.

I would think I could soft start this transformer on a 16A breaker ? or what ?

does timing or the value of the soft-start greatly affect this ?

any suggestions before I kill the breaker with further testing ?



Also one other thing that I have not tested - and I don't intend to test this but mildly curious..

but I have a HV ceramic switch (Radioswitch 86) that I can use to switch between the secondary taps of the ARRL-002-02 transformer. I use WD7S HV-2 board as the rectifier. Is there any inherent danger involved hot-switching the taps ? I assume so - e.g. switching down from a higher voltage ?



73, Benni TF3CY

[K8ERV]

I'm sending some info on slow start by email.

TOM K8ERV Montrose Colo

[KH2G]

I do NOT recommend hot switching HV any time for any reason
Dick

[K1ZJH]

I do NOT recommend hot switching HV any time for any reason
Dick

Secondary high voltage taps into a filter system? I agree. You can get away with this
on the primary under no load conditions--as was done in the SB-220. But at high voltage
i suspect arcing would be a problem.

Pete

[W1QJ]

Secondary high voltage taps into a filter system? I agree. You can get away with this
on the primary under no load conditions--as was done in the SB-220. But at high voltage
i suspect arcing would be a problem.

Pete

No, many commercial ham amps switch secondary taps on the HV (ac) between low and high. There is no real problem with this as long as the switching is not done under load of the amp transmitting. You may want to lower your step start resistance. 20 to 25 ohms should be more than enough. 47 ohms might be too much. There is very little current being drawn on a power supply with no transmit load so you should not being blowing the breaker on start up unless you have a wiring problem or bad diode or cap in the power supply. Bypass your step start resistors ands bring the PS up slowly on a variac and see if there is any humming going on. You might have something shorting. But switching HV (ac) taps on the secondary is a very common thing.

[WX7G]

W1QJ might be right that you have too much step-start resistance. The HV transformer magnetizing current could very well be one to two amps and with 100 ohm total you are not bringing the HV up all the way. I would set the step-start resistance to a total of 10 ohms which will keep the peak current low enough to not trip the circuit breaker.

[AG6K]

W1QJ might be right that you have too much step-start resistance. The HV transformer magnetizing current could very well be one to two amps and with 100 ohm total you are not bringing the HV up all the way. I would set the step-start resistance to a total of 10 ohms which will keep the peak current low enough to not trip the circuit breaker.

 Sound advice. As a rule of thumb the initial inrush-I should be c. 90% of the circuit breaker's rating. Typically this gives under a second before the relay shorts out the step-start R.

[VK4TUX]

220v is LV not HV.

i.e:

IEC voltage range	AC	DC	defining risk
High voltage (supply system)	> 1000 Vrms	> 1500 V	electrical arcing
Low voltage (supply system)	50–1000 Vrms	120–1500 V	electrical shock
Extra-low voltage (supply system)	< 50 Vrms	< 120 V	low risk